Determination of the slope stability have been carried out aiming at the problem of slope instability caused by excess large pore water pressure or the small vertical effective stress.The curve of vertical effective stress and excess pore water pressure of body or a slope foot point over time is analyzed,compared with traditional arc sliding method.It is concluded that the slope stability can be determined by the vertical effective stress or the excess pore water pressure in the design and construction process,which also can be used to monitor the development of slope stability.